(1) Field of the Invention
The present invention relates to solid-state imaging devices and imaging apparatus including the same, and particularly relates to arrangements of bonding pads in solid-state imaging devices.
(2) Disclosure of Related Art
In recent years, endoscopes equipped with solid-state imaging devices which are in the form of chips and include light-receiving parts are widely used for industrial, medical, and other purposes. Industrial endoscopes are useful for, for example, observing and inspecting the inside of machinery, piping, or other objects. Medical endoscopes are very useful for, for example, minimally invasive surgery and gastrointestinal examinations.
Japanese Laid-Open Patent Publication No. 63-303580 discloses an endoscope including a solid-state imaging device. FIGS. 9A and 9B are a side view and a plan view, respectively, schematically illustrating a structure of a conventional endoscope. FIG. 10 is a plan view illustrating a solid-state imaging device in the endoscope disclosed in Japanese Laid-Open Patent Publication No. 63-303580. FIGS. 9A and 9B show an internal structure when viewed through a filler 158.
As illustrated in FIGS. 9A and 9B, the conventional endoscope includes: a lens (camera lens) 151; a prism 152 for bending, to a right angle, the optical axis of incident light 159 which has passed through the lens 151; a solid-state imaging device 153 including an imaging region 154 and bonding pads 155; a board 156 having an upper face on which the solid-state imaging device 153 is fixed; wires 157 whose one ends are bonded to the bonding pads 155 and another ends are connected to, for example, a board (not shown) outside the solid-state imaging device 153; and the filler 158 encapsulating the prism 152 and the solid-state imaging device 153. The shape of this endoscope is tubular.
As illustrated in FIG. 10, a conventional solid-state imaging device 161 includes: an imaging region 154; vertical charge coupled devices (CCDs) 163 provided on the imaging region 154 and used for transferring signal charge read out from photodiodes 162 in the vertical direction (i.e., the left-right direction in FIG. 10); horizontal CCDs 164 placed at a side of the imaging region 154 and used for transferring the signal charge from the vertical CCDs 163 in the horizontal direction (i.e., the up-down direction in FIG. 10); an output circuit 165 for outputting the signal charge from the horizontal CCDs 164; and a plurality of bonding pads 168 provided in a region vertically located to the imaging region 154 and the horizontal CCDs 164 (i.e., a region located at the right side of the imaging region 154 and the horizontal CCDs 164 in the FIG. 10).
The photo diodes 162 are arranged in rows and columns in the imaging region 154. The bonding pads 168 are aligned with a given spacing in the horizontal direction along a side of the solid-state imaging device. The bonding pads 168 receive signals for driving the vertical CCDs and the horizontal CCDs and signals to be supplied to the output circuit 165. Signals from the output circuit 165 are transmitted to the outside of the solid-state imaging device via the bonding pads 168.
The solid-state imaging device 153 is incorporated in the tip of an insertion portion of the endoscope as described above. In particular, medical endoscopes are required to have smaller outside diameters of their insertion portions in order to relieve pain of patients. For this purpose, the insertion portion of the conventional endoscope is provided with the prism 152 for bending the optical axis of incident light 159 to a right angle and is also provided with the solid-state imaging device 153 disposed in such a manner that the direction from the imaging region 154 to the bonding pads 155 coincides with the axis of the endoscope. This structure allows reduction of the outside diameter of the insertion portion.
However, many patients still feel discomfort with gastroscopes and colonoscopies, so that endoscopes with much smaller outside diameters are demanded. In addition, reduction in outside diameter of endoscopes in endoscopic surgery further lessens a burden on patients.
Recent development of integrated circuit technology has greatly reduced the size of imaging regions of solid-state imaging devices. On the other hand, great reduction in size of bonding pads is still difficult because it is necessary to maintain a certain connection strength and an area to be in contact with a probe during inspection. It is also necessary to dispose adjacent bonding pads with a given spacing for, for example, manufacturing reasons, thus making it difficult to reduce the distance between the bonding pads in order to reduce the horizontal width of a solid-state imaging device.